Rectifier



' Aug. 31, 1943.

-c. E. PETERS A 2,328,488

`RECTIFIER Filed Feb. 9, 1942 INVENTOR.

BY @LQ am -the part nunits that consist l and Patented Aug. 31, 1943 Unirse sTliTssl PATENT o FICE 2,328,488 enorm-ma Carl E. Peters,

St. Louis, Mo., assigner to B-L Application February 9, 1942,

Serial No. 429,965

3 Claims. (Cl. 175366) This invention relates to improvements in rectiiiers. More particularly, the invention relates to improvements in methods of cooling dry disc rectiers. A

Dry disc rectiers usually consist of a number of rectifying units that are held together in assembled relation. The rectiers are usually cooled by cooling one part or element of each of the various units. This part of the various rectifying units is usually cooled by placing a heat radiating iin in contact with it. The heat radiating iin has a cross-sectional area that is larger than the cross-sectional area of each part or element of the unit,

conductor of heat and readily conducts heat from Y to be cooled to the ns exposed area where the heat is absorbed by air. In thelcase of dry disc rectifying units that consist of an electropositive element and an electronegative heat radiunit, and the base plate of the second type of' are cooled by spacing them apart from other units of the rectier. This4 is usually a cone-shaped Washer or spacer that abuts against the electropositive element 4or the base plate. This permits air to heat directly from it.

Neither of these methods of cooling is completely satisfactory. In the case `of rectifying spacer is used as the cooling'means, a part of of the electropositive element is covered by it, andJ cannot becontacted by the iin is used as the cooling means,

cooling air. The portion of the element that is covered by the spacer does not receive suicient cooling and may overheat although the rest of the unit is cool enough. From the above, it can be seen that these methods of cooling are not completely satisfactory with this type of rectier. 'I'hese methods of cooling permit overheating of the rectier which is objectionable. of rectifying units of the semi-conductor-type also, these two methods of cooling are not .satisfactory. In this type of rectifying unit, the rectifying surface lies between the electrode and the layer of semi-conducting material. It is, therefore,on thatv surface of the semi-conductor that is spaced away from the base plate. Where a the heat that is generated at the rectifying surface must flow through the layer of semi-conducting material` to the base plate, through the base the contact surface between the the fin, and then f to the periphery of the iin before it can be dissipated. The layer of semiconducting material as its name indicates, is not a good conductor of heat or electricity, and cannot conduct heat very rapidly. As a result, the

plate, through iow of heat from the rectifying surface to the Y melting of the electrode may seriously impair, if

not ruin, the eiiciency of the rectifying unit.

- Where a cone-shaped washer or spacr i's used l positive element.

as the cooling means, the rectifying units also do not get sufficient cooling. The washer or spacer,

an overheating of the surface under the spacer although the rest of thesurfaceis at a safe temperature. These two methods of cooling rectilers can be seen, therefore, to be objectionable in the case of rectlilers of this type also. The invention obviates the objections outlined above by providing a rectifier that has a plurality o! air passages adjacent the velectrode or electro- These air passages foster the dissipation of heat .directly from the electrode instead of indirectly from the layer of semiconducting material, l radiating iin, or foster heat directly from the In the case base plate' and the base plate and the air and the surface to 'the heat in that surface.- Furthermore, the proelectropositive element instead of indirectly from the radiating fin. Heat can be dissipated from the electropositive element itself more readily than it can be dissipated rfrom the combined electropositive element and radiating fin. In the same way heat can be dissipated more rapidly from the electrode itself than it can be dissipated from the layer of semi-conducting material, the

base plate and the,iin, because the heat can flow air that passes over the rectifier at high speed. This problem is encountered particularly in rectiers for use on airplanes. In airplanes, a small stream of high velocity air is conducted to the rectifier and permitted to flow over the rectifier. "I'he rush of this air pastthe rectifier at high speed, might bend the radiating fins whose pe- 'Dry disc rectiers usually consist of a group i of rectifying units that are maintained in assembled relation and are electrically connected together by resilient means. Ordinarily, the resilient means is a cone-shaped washer or spacer that bears against opposing surfaces of the rectifying units. .In the case of a rectifier having a layer of semi-conducting material, one of these surfaces consists of a layer of low melting alloy. As the elements of Athe rectifier expand and contract because of heating and cooling, the end of the cone-shaped Washers move relative to the surfaces of the electrodes. This movement may injure the surfaces of the electrodes, and particularly is this likelywhere the electrode is composed of relatively soft low-melting-point alloy. The ends of the cone-shaped spacers or washers are relatively sharp and may penetrate the l-ayersl of metal that comprise the electrodes. This is objectionable since it materially shortens the life of the rectifier. The invention obviates this objection by providing an improved resilient means. The resilient means provided by the invention permits the units of the rectifier to expand and contract freely without injury. This means is a corrugated member of resilient material. The raised portions of the corrugated member that contact the surfaces of the unit are quite dierent from the ends of the cone-shaped washers. The raised portions of the corrugated member are rounded and cannot injure the surfaces of the units of the rectifier, as the relatively sharp ends of the cone-shaped washers may do. The use of the corrugated member of resilient material provided by theinvention, therefore, may increase the life of the rectifier. It is, therefore, an

object of the present invention to 4provide a corrugated member of resilient material for rectiflers.

The provision of corrugated members of resil- `ient material for rectiers is quite desirable.

' Ihese corrugated members permit eilicient cooling of the rectiers, by providing a plurality of vpassages for air adjacent thesurface to be cooled.

direct contact between the be cooled that dissipates These passages permit vision of these passages facilitates efcient cooling of the rectiers without increasing the crosssectional areaofthe rectifier. Where heat radiating finsare used in a rectier to facilitate heat radiation, angincrease is had in the cross-sectional area of the' rectifier that is accompanied by a decrease in the rigidity of the rectifier. This is objectionable where the rectifier is cooled by plate for rectiflers ripheries extend out beyond the peripheries of the other elements of the rectifier. Such bending would short circuit some of the recti-fying units. This is objectionable because it would materially decrease the capacity of the rectifier. The invention obviates this objection by providing a plurality of passages next to the cooled, that permit the making of a compact and strong rectifier. It is, therefore, an object of the present invention to provide a strong compact rectier by having a plurality 0f passages thereinfor air.

The corrugated members of resilient material provided by the invention, are more desirable than the cone-shaped resilient spacers now in use. The cone-shaped spacers entrap air next to the surface to be cooled and since this entrapped air cannot escape up. In the case of a rectifier having a layer of semi=conducting material, this heating may result in a melting of the low melting point alloy electrode under the cone-shaped washer, although the rest of the electrode is relatively cool. This cannot happen with rectiflers that are provided with the corrugated resilient member of the invention, because such a member prevents the entrapment of air.

Present day rectifying units of the semi-conductor type consist of a base plate that has one surface covered with a layer of the semi-conducting material and has the other surface bare for radiation purposes. The ypresent invention provides a rectifying unit of the semi-conductor type having a base plate with a layer of semiconducting material on both surfaces. This can be done because the invention does not rely on the base plate for heat radiation. Because the base plate has two terial on it, it has twice the rectifying capacity of present day base plates. It is, therefore, an object of the present invention to provide a base having a layer of semi-conducting material on each surface.

Other objects and advantages of the invention will appear to those skilled in the art from an examination of the drawing and accompanying description.

In the drawing a-nd accompanying description, a preferred form of the invention is shown and described, but it is to be understood that the drawing and accompanying description do not limit the invention and the invention will be defined by the appended claims.

In the drawing,

Fig. 1 is a perspective view of a plurality of rectifying units, and

. Fig. 2 is an end elevational view of a rectifier made in accordance with the principles of this invention.

Referring to the drawing in detail, the base plates of the rectifying units are denoted by the numeral lil. Supported on these base plates are layers l2 of a semi-conducting material. This senil-conducting material will preferably be sele surface to be y it will continue to heat layers of semi-conducting maf 2,328,488 low melting point alloy. The rectifying surface of the rectifying unit lies' between the electrode and the layer of semiconducting material. This suriace is cooled quite emciently by the vmovement of air through the passages formed by the corrugated members I6 and the surfaces of the electrodes i4. Part of this air contacts lthe metal of which the corrugated member is composed, and absorbs heat from it. In this Way, heat is removed directly and indirectly from the electrode, and the temperature of Athe electrode and the rectifier is kept at a safe level.

Each rectifying unit comprises a base plate ld, a layer i2 of semi-conductlng mateiral, and an electrode l5. In some cases as shown, a base plate lll may have two layers i2 of semicon ducting material and two electrodes lll. These rectifying units must be held in electrical engagement, but must be permitted to more rela tive to each other as they expand and contract due to' heating and cooling. The corrugated member it of resilient material is quite ativann tageous because it provides the necessary resilience as Well as the necessary electrical contact.

The corrugated member is particularly useful because it has a large surface area for radiation purposes, and because: its raised portions are rounded and can move relative to the surface of the electrode lll without injuring it. As a result, the corrugated member i6 provided by the invention is more washers and spacers used heretofore. This corrugated member it should be al good conductor of electricity and should have a reasonable amount of resilience. Brass and copper can be used to advantage and a number oi other metals can also be used..

The 'base plates ill are connected together by suitable electrical leads that are indicated gen erally by the numeral il, and' the resilient memadvantageous than the cone-shaped bers l t are connected together by electrical leads that are indicated generally by the numeral il. From this, it can be seen that the resilient members i5 not only serve as heat dissipatore and resilient means, they serve as electrical contacts.

A number oirectifying units can be assembled to form a rectifier similar to Vthat shown in Fig. 2. This rectiner is encased in a housing that consists of a top it, a bottom 2i) and sides 22 and is suitably insulated from the elements of the rectiiier. The housing is encased in a frame consisting of plates 2d and 26 and nuts and bolts 28. .l The sides 22 of the housing are so dimensioned that when nuts 2B are tightened, the resilient members l5 will be compressed sumciently to insure the maintenance of good contact between the rectifying units. 'This housing may be connected to an air duct that will conduct air to the rectifier. This air will cool the rectiiler eiiectively by absorbing heat from the electrodes and the resilient members. The air will absorb heat directly from a part of the surface of the electrode, and indirectly irom'the rest of the surface of the electrode by absorbing heat from the corrugated member that is in contact with the electrode. It will be noted that this construction obviates the use of the bolt usually found in the center of dry disc rectiiers. This bolt would interrupt the ilow of air across the surface to be cooled and would causev a turbulence or air that would decrease the cooling -eii'ect given by the air. In the construction shown, there is no such obstruction to the fiovf` of air and the air ows smoothly through the passages.

The size or", the corrugations on the members l t will be determined by the use to which the rectifier ,is put. For instance, ii the rectifier is used on airplanes, the corrugations must be small and must be close together. In an airplane, the rec\ tiiler will be supplied with a small amount of air at relatively high pressure. Because the supply oi air is small, the ratio of the surface area of the passageway to the volume oi the passage- Way must be as large as possible; and the flow oi air must be as smooth as possible, to permit maximum emciency ln transferring heat from the 'electrode to the air. Where larger volumes ci air are available at 'lower pressures, the passages are made somewhat larger.

Although such rectiners have not been shown in the drawing, the invention also contemplates the use oi corrugated members oi resilient material with rectiiying units comprising electropositive and electronegative elements. These rec tiiying units will be separated from each other by the corrugated member or the invention, and can be cooled by air passing through the passages formed by the corrugated member and one sur face of the rectiiying unit. lily use or the cor= irrigated members, a strong, compact, and readily cooled rectifier can be made.

ln the drawing and specillcatlon, a preferred form oi the invention has been shown Aand described, but it is obvious to those skilled in the art 'that various changes may be made in the form of the invention Without ailecting the scope oi the invention.

l. A rectiier comprising a plurality of rectifying units, a corrugated metallic member, and means to maintain the units and the member in assembled relation, each oi said rcctifying units comprising a base plate, at least one layer oi semi-conducting material having one or its surlaces in direct Contact with said base plate and at least one electrode of relatively low melting point metal in direct contact with the other surface ci said semi-conducting material, said corrugated member being of resilient metal and having a plurality of smoothly rounded corrugations, said units and said member being assembled so the electrodes or said units face each other and dlrectly contact the smoothly rounded corrugan tions of said corrugated member whereby corrugated member electrically connectsI said electrodes while it reslliently spaces them apart to permit air to .directly contact the major portion of the surface of the electrodes and to directly contact the corrugated member. l

2. A high capacity, compact selenium rectifier comprising a plurality of selenium rectifying units, a corrugated metallic spacer and a frame maintaining said units and said spacer in' assembled relation, each of said selenium rectifying units comprising a bese plate, at least one layer of selenium having one of its surfaces directly in contact with said base plate and at least one spray metal electrode in direct contact with the other surface of the selenium, said corrugated spacer being made of resilient metal and being corrugated to be compressble, said units and said spacer being assembled so the units are oppositely disposed of said spacer and the electrodes of the units contact said spacer, said frame being climensioned so said spacer is compressed, said spacer being arranged to electrically connect said spray metal electrodes and to resiliently space them apart so air can contact the major portion of the surface of said electrodes.

3. A rectifier comprising a plurality of rectifysaid 4 ascuas ing units, a corrugated metallic member, and can directly contact the major portion of the surmeans to maintain said units and said member in faces ofv said electrodes, said smoothly rounded assembled relation under pressure, each of said corrugations being arranged to permit relative rectifying units having at least one electrode of movement between the electrodes and the correlatvely soft metal, said corrugated member be- 5 rugated member without injury to said electrodes, ing made of resilient metal and being corrugated vsaid pressure maintaining means being arranged to be compressible and to leavel a plurality of to compress said corrugated member and thereby smoothly rounded corrugations, said units and maintain 'pressure between said member and said member being assembled so the corrugated` said units.

member provides a pluraliy of line contacts be 10 CARL E. PETERS. tween the electrodes on said units, and so air l 

